The present invention relates to detergent additives and detergent compositions. A detergent additive is a product designed to supplement the consumer's ordinary detergent product to boost the latter's effectiveness. The detergent composition aspect of the present invention encompasses the detergent additive aspect with the additional feature of having present a surface active agent in the composition.
Alkali metal orthosphosphates function as detergent builders by precipitating calcium ions on a 2 to 3 mole basis respectively. The orthophosphates of the present invention are not as effective in building capacity as the pyrophosphates discussed below and in the concurrently filed U.S. patent application Ser. No. 550,054 for Cherney and Hau (attorney's Docket Number 2174) herein incorporated by reference. However, soluble ortho phosphates provide a distinct advantage in the present invention of providing whiteness maintenance. The distinction between whiteness maintenance and building capacity is that in the former, the tendency of washed fabrics to pick up suspended soils from the wash solution over a number of wash cycles is measured by the reflectance of light. Builder effectiveness is measured by the ability of the orthophosphate or other builder material to control hardness so that soiled fabrics may be cleaned in the first instance. Builder effectiveness is also measured by light reflectance on the fabrics that are washed and dried. The importance of builder effectiveness and whiteness maintenance may be demonstrated by washing a heavily siled white towel with a lightly soiled towel. When both towels are cleaned in a wash cycle the wash water is drained through the towels prior to the rinse step causing the suspended soils from the heavily soiled towel to be deposited on the lightly soiled towel. Often the suspended soils are harder to remove from the fabrics than to remove the soil from the fabric initially. Over a number of cycles the suspended soil building up causes white articles particularly terry cloth to gray or become dingy.
Those skilled in the detergency arts have also for many years equated the alkali metal pyrophosphates with the alkali metal tripolyphosphates in detergent compositions. It is known that pyrophosphates and tripolyphosphates when used as builders will each sequester one mole of calcium or magnesium water hardness per mole of the phosphate species. Pyrophosphate detergency builders, however, unlike tripolyphosphates will under certain conditions form minor amounts of dicalcium pyrophosphate a completely neutralized insoluble salt. The precipitation of the pyrophosphates discussed above may take place on the fabrics being cleansed or upon the surfaces of the washing machine. Such buildup of the calcium pyrophosphate salt is undesirable in that the precipitates have a tendency to remain on the fabrics through several wash cycles and continue to buildup thus causing harsh fabric. Similarly, the calcium pyrophosphate will after several cycles in a washing machine cause unsightly deposition or scale on the exposed surfaces. This precipitation phenomenon of the pyrophosphates has led many detergent manufacturers to avoid pyrophosphates and to instead use tripolyphosphates.
It has been suggested in U.S. Pat. No. 2,381,960 to Johnson issued Aug. 14, 1945 that the effectiveness of sodium pyrophosphate in reducing water hardness could be obtained by adding the pyrophosphate to the solution of hard water after an alkaline material had been first added to the water. The alkaline materials taught by Johnson were sodium orthophosphate, sodium and potassium hydroxide, sodium and potassium carbonates, and sesquicarbonates, soap and sodium silicate having an SiO.sub.2 :Na.sub.2 O weight ratio greater than 1.5. The point of addition of the tetrasodium pyrophosphate to the solution is stated to be prior to the formation of a macroscopic precipitate of the hardness ions and the aforementioned alkaline materials.
In U.S. Pat. No. 2,326,950 issued Aug. 17, 1943 to Kepfer, it is taught that tetrasodium pyrophosphate is used more efficiently to control water hardness when it is used in conjunction with an alkaline material which is added to the solution before a macroscopic precipitate of the hardness ions and the pyrophosphate is formed. The alkaline materials taught by Kepfer are sodium borate, sodium metasilicate (SiO.sub.2 :Na.sub.2 O 1:1) and disodium hydrogen phosphate. The processes of controlling water hardness by somehow increasing the effectiveness of sodium pyrophosphate taught Kepfer and Johnson, herein incorporated by reference, suffer from the defect that the composition could not be effectively prepared without going to the trouble of positively insuring the delay of the pyrophosphate relative to the alkaline materials or vice versa. Thus Kepfer and Johnson could only with great difficulty be adapted for use in granular or liquid products which are favored by the consumer today.
U.S. Pat. 3,708,428 issued Jan. 2, 1973, to McDonald discusses the neutralizing of organic detergent acids such as alkyl benzene sulfonic acid with sodium silicates having an SiO.sub.2 :Na.sub.2 O ratio of from about 1:2 to about 1:4 to form an in situ silica having an SiO.sub.2 :Na.sub.2 O ratio of from about 1:4 to about 1:2000 or greater. An essential condition to the compositions taught in McDonald is that the inclusion of water soluble alkali builders, illustrated by sodium or potassium orthophosphates, or complex phosphates (i.e. pyrophosphates), alkali carbonates, borates, silicates, or neutral salts, such as sodium chloride or sodium sulfate, or magnesium sulfate, be restricted to levels of concentration of the order of 4% by weight or lower. McDonald goes on to state the desired advantages of the in situ formed colloidal silicas on the removal of soils will be found to be appreciably impaired if the foregoing limits ae not strictly adhered to.
It is thus an object of the present invention to utilize an alkali metal orthophosphate more efficiently in the control of water hardness and whiteness maintenance.
It is a further object of the present invention to prepare a composition utilizing an alkali metal orthophosphate as a detergency builder that minimizes the buildup on fabrics of water insoluble orthophosphates.
It is yet a further object of the present invention to provide a detergent additive product or a complete detergent composition built with an alkali metal orthophosphate which is particularly effective in cleaning and whiteness maintenance.
It has now been found that by preparing a detergent additive comprising an alkali metal orthophosphate and silica or a complete detergent composition comprising the alkali metal orthophosphate, silica and an organic detergent component that the objects of the invention may be achieved.
Moreover, the use of the alkali metal orthophosphate with the silica of the present invention in an additive or detergent composition substantially decreases the amount of calcium ion in the wash solution. While not wishing to be bound by any particular theory it is the applicants' belief that silica in some manner encourages the precipitation of calcium ions in the wash solution as insoluble calcium orthophosphates.
Particularly effective compositions of the present invention are prepared by using both soluble orthophosphates and pyrophosphates such that both phosphates precipitate water hardness in conjunction with the silica. These mixtures of pyrophosphates and orthophosphates must be in a respective weight ratio of 1.5:1 to about 1:4, preferably about 1.5:1 to about 1:2.5, most preferably about 1.5:1 to about 1:1.5. The ratio 1.5:1 above is important in that undersirable fabric feel occurs at higher ratios. Thus, where prior art compositions pyrophosphate salts were only able to effectively sequester on a 1:1 mole basis with calcium hardness, the present invention allows the pyrophosphate to effectively control twice the amount of calcium which is possible by sequestration. The precipitation of the dicalcium pyrophosphate takes place with the aid of the silica such that the precipitated salt does not form an unsightly scum on the exposed surfaces of the washing machine or deposit on fabrics to cause a harsh feel. The more effective control of calcium ion in the wash solution means that the detergent components are not as likely to be interfered with by the water hardness in the wash thus providing better cleaning of the fabrics.
Soluble silicates are often added to detergent or additive products to protect exposed machine surfaces from corrosion. It has been found, however, that soluble silicates interfere with the precipitation of calcium hardness as dicalcium pyrophosphate and as the calcium orthophosphates. Other components found in detergent products have also been found to interfere with calcium precipitation as the ortho and pyrophosphate salts, namely the detergent active.
It has now been found that the addition of silicas to the additive or detergent product diminishes the tendency of soluble silicates and other components such as the detergent to interfere with the precipitation of calcium ortho and pyrophosphate.
Throughout the specification and claims percentages and ratios are by weight and temperatures are in degrees Fahrenheit unless otherwise indicated.